The invention relates to a system for lifting and supporting an object; particularly to a two part jacking system including a power unit that can be used to place and elevate a jack stand for lifting and supporting a corner of a vehicle. The two part system is inherently safer to use than a conventional floor jack to elevate a vehicle, and which then requires the user to crawl under the vehicle to try to place a convention jack stand adjacent to the elevated floor jack to support the load. The inventor of the present invention is a pioneer of the two part jacking system and holds numerous patents related to this technology.
Briefly, the two part jacking system consists of a mobile hydraulic power unit having a flat front base and extendable lift arms with leveling pads; and a set of separate mechanical jack stands that can be secured within the front base of the power unit, and elevated by extending the lift arms of the power unit, and locked by an integral ratchet locking mechanism. An example of the two part jacking system describing the power unit is shown in U.S. Pat. No. 7,410,148 (see FIGS. 1 and 9); and an example of the jack stand is also shown and described (see FIGS. 2-8).
In use, the jack stand is engaged within (and can be disengaged from) the front base of the power unit, and is maneuvered into position, i.e. under a vehicle, to place the stand in a desired location for lifting and supporting the vehicle. The power unit is activated by pumping the handle, raising the lift arms, and the stand is thereby extended vertically to the desired height, locked in position, thus lifting and supporting the vehicle on the stand. By operating the controls at the end of the handle, the power unit lift arms are lowered, and the power unit is disengaged from the stand and pulled away, leaving the stand in position supporting the vehicle. The power unit is then free to position and extend another stand for elevating another corner of the same or another vehicle.
To lower the vehicle and remove the stand, the power unit is maneuvered into position to re-engage with the stand. By operating the controls at the end of the handle, the power unit is re-engaged with the base of the stand and the lift arms are elevated to the height of the extended jack stand. The controls can then be operated to disengage the ratchet locking mechanism of the stand, and the lift arms are released to lower the stand to its original position. The power unit remains engaged with the stand and can be pulled away from the vehicle with the stand carried within the base.
The early design of the power unit and jack stands were for consumer use, and has later evolved also into commercial use. The commercial use requires higher capacity of 3-4 tons for heavier cars and trucks with many duty cycles of use each work day. The prior system was improved with heavier gauge materials, but had a relatively short life due to failure of one or both of the leveling pads or frusta-conical roller bearing on the leveling pad, for lifting the jack stand supporting the load. The leveling pads and the roller bearings were repairable, but it has been determined to improve the design for the required capacity and extended life for commercial use.
The early designs of the power unit were adapted to carry up to four jack stands within the base; current models carry only one or two stands. Additional stands could be acquired to reload the power unit, so that a single power unit could be utilized to efficiently place and actuate numerous stands. Many commercial users employed the system for multiple ongoing projects, and would utilize all of their available stands. The power unit was thereafter useless until another stand was available, from a completed project, to be extracted and reused on a new project.
The present inventor developed a “bridge” lifting plate positioned to bridge between the forward ends of the lift arms and adapts the power unit to function as a hydraulic floor jack, to more fully utilize the power unit. The present inventor also developed a bridge plate that could travel along the lift arms, and that was biased by compression springs toward the forward ends of the lift arms and onto the leveling pads to provide an “automatic slide forward bridge”. The vertical housing of the jack stand(s) would force the bridge rearward on the lift arms. When there were no more stands within the base of the power unit, (and when the lift arms were in the lowered position) the bridge would automatically slide forward onto the leveling pads at the forward ends of the lift arms. The power unit then functioned directly as a hydraulic floor jack.
The automatic slide forward bridge mechanism has been revised to include various design improvements. An example of a recent improvement is described in U.S. Pat. No. 7,410,148 (see FIGS. 32-34). This prior art bridge mechanism utilized a pair of compression springs enclosed within pairs of telescoping tubes to bias the bridge toward the forward ends of the lift arms.
This improved prior art design was functional, but did not always reflect the sliding reliability and durability as desired for the system, particularly for commercial applications of the system. Due to component variance, time and wear, the forces exerted by the compression springs were not always equal. The use of compression springs to bias the bridge forwardly required alignment and support of the springs by the telescopic tubes. Once a compression spring or one of the surrounding tubes became kinked or distorted, it needed to be replaced. Tension springs tend to be less expensive, self aligning, durable and do not require telescopic tubular side support. It was determined that the mechanism would be more reliable and durable if the bridge could be biased forwardly utilizing tension springs.
The various designs of the automatic slide forward bridge included a continuous bias forward of the bridge every time a jack stand was released from the power unit. In most cases, the power unit would be used sequentially with another jack stand and the bridge was not required or desired. This produced unnecessary wear on the bridge mechanism and continuous effort by the next jack stand to reposition the bridge rearward in the lift arms. It was determined that a latching system to retain the bridge in the middle position (rearward of the jack stand) was needed, until it was desired to release the bridge and utilize the power unit as a load lifting jack.
The use of a slide forward bridge with the power unit acting as a floor jack is best utilized with a safety mechanism to lock the elevated lift arms in position, in the event of any decay of hydraulic pressure while elevated. Such a device is described in U.S. Pat. No. 7,413,169 (see FIGS. 35-37). The device was automatically deployed every time the lift arms were raised, and required release by a separate control lever to lower the lift arms. This resulted in a problem in that the operators would sometimes forget to release the lever and the lift arms were locked in position until the operator remembered the control lever.
Another problem was presented for the jack stand due to the redesign to improve the operation of the automatic slide forward bridge. The bridge has been designed to slide along the lift arms at a more rearward position and the vertical base (or lifting plate) of the jack stand did not force the bridge sufficiently rearward to reposition the jack stand within the base of the power unit. It was determined that an elevated extended bumper was required on the vertical base of the jack stand.
The redesign of the system of the present invention resulted in a power unit having only one jack stand and a larger slide forward bridge mechanism within the base. Commercial user required numerous jack stands within the shop, and also included some mobile service to remote sites for vehicle service and repairs. It was necessary to transport two or more jack stands to various location for use with the various power units. It was determined that a mobile rack was needed to efficiently transport the jack stands required for use by the power unit.
In view of the foregoing problems, it is an object of the present respective invention to provide an improved power unit with leveling pads having a capacity of at least 3 tons and extended use;
It is another object to provide a power unit having an improved slide forward bridge mechanism having a capacity of at least 3 tons that is precisely aligned, smoothly operated by tension springs, and reliable and durable in operation.
It is another object to provide a power unit having a releasable latch mechanism for retaining the slide forward bridge in the middle position of the lift arms, until needed;
It is another object to provide an improved power unit having a safety mechanism for securing the lift arms when the slide forward bridge is in use, and which is automatically released when the lift arms are lowered;
It is another object to provide a jack stand that effectively pushes the slide forward bridge into the middle position when the jack stand is positioned into the front base of the power unit;
It is another object to provide a jack stand having a base plate that facilitates securing the jack stand into the mobile rack; and
It is another object to provide a mobile rack for transporting two or more jack stands to various locations for use by the power unit.